Follow-up of GSTM1, GSTT1, and NAT2 genotyped patients with knee or hip replacement

A total of 147 patients, genotyped for glutathione S-transferases M1 (GSTM1) and T1 (GSTT1) and for N-acetyltransferase 2 (NAT2), who had undergone total joint replacement of the knee or hip joint between August 2004 and June 2007, showed with 45% a remarkably lower portion of the GSTM1-negative genotype compared to both a local control (51%), an external control (52%) and the portion reported in the literature for the European population (50%). In contrast, the portions of GSTT1-positive (84%) and slow NAT2 (55.1%) patients of the initial collective were unremarkable, compared to both controls. To elucidate a possible impact of this interesting finding on the long-term outcome, the patients were contacted in December 2015. Afterwards, they were interviewed using a self-prepared questionnaire. The average follow-up time was 9 years. At the time of follow-up, 57 patients were deceased, 46 patients did not respond and 12 patients declined the interview. A total of 32 patients participated in the follow-up. The mean age of the followed-up patients was 75.9±8.3 years, whereas the mean age of all patients at the time of surgery was 70.9±9 years. The portions of the GSTM1-negative genotype (15 out of 32; 47%), the GSTT1-positive genotype (24 out of 32; 75%) and the slow NAT2 status (17 out of 32; 53%) in the followed-up patients were comparable to those of the initial collective. The follow-up results of the patients after 9 years were unable to clarify the significance of the observed lower portion of GSTM1-negative patients. In view of a recently published omics study reporting a reduced GSTM1 activity in tissue attached on hip implants explanted due to aseptic loosening, the striking portion of the GSTM1-negative genotype in this present study may encourage further investigation into the impact of this gene in patients with hip or knee replacement.